No abstract

Environmental factors such as climate change, temperature fluctuations, and mechanical forces hinder long-term space, transportation, and research missions due to structural damage. We report an innovative system to overcome this problem. The self-healing structure under examination is an epoxy as a polymeric matrix, which includes microcapsules embedded with epoxypolydimethylsiloxane (PDMS), as a healing agent, separately combined by microcapsules embedded with triethylenetetramine (TETA) as a hardener or curing agent. Scanning electron microscopy confirmed the presence and size of the microcapsules. It was shown that the rough appearance of microcapsules improves mechanical bonding. The diameter of microcapsules varied between 40 and 200 μm, with an average diameter of ~100 μm. The information of microcapsules and their structures were scrutinized through Fourier transformed infrared spectroscopy for chemical structure confirmation. It was determined that epoxy-PDMS practical liquids have been effectively encapsulated. The thermal performance of the microcapsules was investigated utilizing thermogravimetric analysis. The results showed that the microcapsules have thermal stability up to 220 C without degradation and decomposition. Additionally, the flexural test was used to evaluate the samples manually scratched with blade and compared with the pure epoxy sample. The results showed the sample containing 15% microcapsules has 105% recovery efficiency after 55 h.

In the present study, we introduce an innovative procedure to manufacture engineered hybrid composite composed of epoxy resin as the polymeric matrix, carbon fibers, and poly urea-formaldehyde (PUF) microparticles. An ultrasonic probe was utilized to achieve a uniform molecular combination of the epoxy resin and PUF microparticles. Emulsion polymerization was also used in this research to synthesize micro-polyurea formaldehyde powders. Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), tensile, and three-point bending assessments were implemented on unfilled, 2, 5, 10, and 13 wt% PUF microparticles filled epoxy resin to identify the loading influence on the diffusion rate, as well as the mechanical and thermal performance of the hybrid composite structure. The results of the flexural test show that both strength and modulus increased with a growing loading proportion of PUF microparticles. Moreover, optimum properties were achieved by adding 10 wt% microparticles. The results of the TGA demonstrate that the thermal behavior of the composite structure is sensitive to the PUF microparticles content. Based on the experimental data, the tensile test has also shown optimum behavioral properties through increasing the level of micro-particles in the sample E-40, which is due to the appropriate, uniform, and advanced composition of particles, matrices, and fibers. In addition, we used Fick's Law to determine the gas diffusion and mass transfer rates for samples at different temperatures. The gas absorption test revealed that the enhanced hybrid system behavior can be an obstacle to water and moisture.